Engine Indicator Diagrams

Indicator diagrams indicates, simultaneously , the pressures and the relative position of the piston for a particular engine cylinder. They are taken for every voyage, both in loaded and ballast condition. It is a practice to take indicator cards after every major overhauls.

Purpose

To calculate indicated power of the engine

To determine peak pressures and compression pressures

To evaluate the process of combustion inside the engine

To evaluate scavenging and exhausting conditions

Procedure

Check whether the spring fitted on the indicated instrument will meet the peak pressure (maximum combustion pressure) to be expected

Stretch diagram paper firmly over the drum.

Before taking diagram, open indicator cock, allow two or three firing strokes, to blow out soot and combustion residues in the cock.

After drawing atmospheric pressure line, hook the cord to indicator drive, open indicator cock, take power card and shut off the cock.

Make sure that the instrument is not exposed to high temperature for long time. This may affect its accuracy.

Remove the hook, turn the drum by hand to a place clear from the power diagram, take compression pressure line with the fuel cut off.

After taking indicator cards from all the cylinders, open the instrument and clean all the parts, and lubricate the same.